Electrical coil



June 21, 1938. E. DIETZE ET AL 2,120,973

ELECTRICAL con,

Filed March 11, 1936 E. DIE TZE INVEMZRSJWFOLEY ATTORNEY Patented Junez l, 1938 c I UNITED STATES PATENT OFFICE ELEGTRICAL COIL vlilginhard Dietze, Westfield, and John W. Foley, Englewood, N. 1., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application March ,11, 1936, Serial No. 68,228

\ Claims. (01.179-173) This invention relates,to electrical coils, and, which is divided into two sections by a magnetic more particularly, to that class of coils used in shield member. telephone substation circuits. Another feature comprises an electrical coil An object of this invention is to provide an having three superposed windings, one of which 5 electrical 'coil in which is combined effectively the is divided. into two sections, one section being 5 usual transformer and abalancing network in an, closely coupled to the other windings and the antiesidetone telephone circuit. other section being loosely coupled thereto.

It is well known that, to properly balance any. A further feature comprises an electrical coil anti-sidetone substation circuit so that there will comprising a plurality of windings, one of which is be no sidetone in the receiver of the transmitdivided into'superposed sections by a magnetic ting station when transmitting, it is necessary shield member. that the combined impedance of the components Other and further features will be evident-from or elements forming that portion of the circuit the detailed description which follows hereinwhich provides the balancing network have the after. v. phase angle as that of the line to which A more complete understanding of this inven-. 15 the set is connected as well as a certain definite tion will be obtained from the following descripratio between the absolute magnitudes of the im-. tion taken in conjunction with the appended pedances of the line and the network. In some drawing wherein: types of anti-sidetone circuits ordinarily em- Fig. l is a side view, partly broken away and 30 ployed for common battery lines, the condenser in sectlon, of an electrical coil embodying the inwhich is used to confine the direct current to a vention;

path through the transmitter, although not com- Fig. 2 is a sectional view of the device of Fig. l, monlyconsidered as such, forms a part of the along the line 22 thereof; and v balancing network and, hence, introduces a nega- Fig. 3 is a schematic of the device of Figl 1 to iii telephone lines have practically a zero or a posi- The device of Figs. 1 to 3 is an electrical coil tive phase angle, it'is apparent that the proper l0 embodying an induction coil and a retardation phase angle cannot be given-to the balancing coil. for use in an antl-sidetone telephone subnetwork for these lines unless the effect of -the station circuit. 'It comprises insulating end condenser is counteracted or minimized. This pieces at the ends of and supporting a core 0 maybe done in either of two ways: ('1)' by ad- I2 of magnetic material, such as silicon steel. vA justing the capacity of the condenser, or (2) by' first winding I3 is wound about the core, a secinsertlng an inductance element in the network." 0nd Winding is Wound about the s and a w a positive phase angle is sired, only the third winding I5 is wound about the second, the latter method would be effective. In cases where windings. being. separated by layers of '35 the phase angle is small, relatively .large values sulating The third winding is divided into of capacity would be required since the mast; two portions or sections l1, It by a sheet metal tude of the network is small as-compared to the 40 impedance of the line. The; usualmethod of inserting-an inductance would be to use a separate retardation coil This, taken in conjunction with siliconsteel or permalloy, which may bedlvided The portion I I of winding l5, it is evident, is closely coupled to the first and'second windings .the usual Induction coil, would be relatively exfunctions with m as tran form r A p s v v. r induction coil in the usual manner. The portion Another object of this invention therefore is to g functions in part as a retard inductance and, 45

' provide a single electrical coil that performs in other part, is coupled to the other windings c eap y and effectively the electrical functions of of the coil, the closeness of coupling being deteran induction coil and a retardation coil. mined by the proportions of the shield. In addi- A feature of this invention comprises an election, the amount of inductance may be varied and trical coil having a plurality of windings .one of' the ratio of transformation with windings l3, ll 50 tive reactance. Since many common battery show the'relation of the various windings thereof. 25

shield or spacer l9 of'magnetic material, such as I into substantially semi-cylindrical sections 20. .v

may be controlled by variation in the number of turns in each section of the third winding. If desired, an additional shield 2| of magnetic material may be placed around the outer section of winding I! to more completely isolate it from the other windings.

The formulae for designing the winding I! to obtain an uncoupled inductance are as follows:

where:

C is the self-inductance of winding i5.

C1 is the self-inductance of section ll of winding l5.

C2 is the self-inductance of section l8 of winding l5.

L0 is the inductance desired to be uncoupled from the other windings.

k is the coupling factor between the section I! and other windings-of the coil.

k k" are constants expressing the relation between the number of turns m, n: and the inductance C1, C2 of the sections of winding l5.

While this invention has been described with reference to a specific embodiment, it is to be understood that it is capable of other embodiments and that the invention, therefore, is limited in scope by the appended claims, only.

What is claimed is:

1. An electrical coil comprising a magnetic core, a first winding wound on said core, a second winding wound directly around the first, and a third winding comprising two sections separated by a shielding element of magnetic material, one section being wound directly on said secondwinding and the other on said shielding element.

2. A combined induction coil and inductor comprising a cylindrical core of magnetic material supported at its ends by blocks of insulating material, at least three windings wound in concentric layers over said core and between said blocks, and a cylindrical shield of magnetic material for.

over said first portion, and a second portion of said third winding over said shield.

3. An electrical coil device including transformer "and inductive impedance portions, substantially mutually independent magnetically but embodied in the same unit structure, said device comprising a core, a shield, each of magnetic material, and a first, second and third winding said first winding being wound directly on said core, said second winding being wound directly over said first winding, a first portion of said third winding being wound directly over said second winding, said shield lying over said first portion, and a second portion of said third winding being wound over said shield.

4. A combined induction coil and inductor comprising a core of magnetic material, a first winding wound on said core, a second winding wound over said first winding and inclose coupled relation thereto, a shield of magnetic material, and a third winding having two portions,

one of said portions being wound over said second ,winding and closely coupled thereto and the other of said portions being separated from said one portion and the other windings by said shield.

5., A combined induction coil and. inductor comprising a core, a shield, each of magnetic material, and a first, second and third winding, the 1' first winding being wound on said core, the second winding being wound directly over said first winding, a portion of said third winding being wound directly over said second winding, the

shield being over said first portion, and a second portion of said third winding being wound over said shield, whereby the first and second windings and the first portion of the third winding constitute an induction 'coil and the second portion of the third winding constitutes an inr ductor.

EGINHARD DIETZE. JOHN W. FOLEY. 

